DESCRIPTION: Physiologically based models of human stereomatching have proposed two ways to remove depth ambiguity in the responses of single units. In one, the disparity range is related to the spatial scale of the detector. In the second, different scales interact to remove residual depth ambiguity. The investigator proposes a set of psychophysical experiments to test whether these rules are used in human vision. A second set of experiments will test whether large diplopic disparities are processed by different mechanisms than those involved with fine stereoacuity. An understanding of normal stereovision is a prerequisite for an understanding of abnormal development of binocular vision, effects which include both strabismic and anisometropic amblyopia.